Dual mode communication devices are communication devices configured for communication such as radio communication in more than one communication mode. For example, such modes of communication include digital and analog signaling, different frequency bands for communication, and communication according to different communication protocols. Examples of such protocols are Advanced Mobile Telephone Service (AMPS), North American Digital Cellular service according to J-STD-009, PCS IS-136 Based Mobile Station Minimum Performance 1900 MHz Standard and J-STD-010, PCS IS-136 Based Base Station Minimum Performance 1900 MHz Standard ("IS-136"); Code Division Multiple Access (CDMA) radiotelephone service according to EIA/TIA interim standard 95 Mobile Station-Base Station Compatibility Standard for Dual-Mode Wideband Spread Spectrum Cellular System ("IS-95"); Global System for Mobile Communication ("GSM"); and satellite protocols such as that proposed by Iridium, L.L.C. ("Iridium;" Iridium.RTM. is a trademark and service mark of Iridium, L.L.C.). A typical communication system provides communication in one of these modes in a limited geographical area. A dual mode communication device may use one or more of these modes for communication.
Existing dual mode radiotelephones include some cellular telephones. For example, cellular phones according to IS-136 and IS-95 are operable in both an analog mode and a digital mode. Cellular phones according to IS-136 are dual band communication devices in that they operate in a first band of frequencies near 800 MHz and a second band of frequencies around 1900 MHz. Such radiotelephones communicate with a single type of communication system in different modes.
Such previous radiotelephones are constrained by the limited geographic coverage of the system. When the radiotelephone is moved to a new area beyond the system's boundaries, service on the radiotelephone is no longer available. Even though other systems provide service in the new area, unless that service is compatible with the radiotelephone, the radiotelephone can't communicate with the system. Further, service on a system may not be available for a time. Even though other (incompatible) systems provide service to the same area, the radiotelephone is not usable.
A new type of radiotelephone is envisioned which can operate on multiple, independent communication systems. Thus, in a particular area, a radiotelephone of this new type may communicate with a terrestrial system such as a GSM system and with a satellite system such as an Iridium system. In a different area, the radiotelephone may communicate with two terrestrial systems.
Market demands for radiotelephones usable on satellite and next generation cellular systems require them to operate on multiple cellular systems in a dual product format. However, an integrated approach where a single hardware and software architecture is designed to handle many modes of operation is very costly in terms of engineering effort and time to market. Such a development effort may take more than a year. Given the significant size and cost restrictions now occurring in the radiotelephone industry, a simplified approach to new product development becomes necessary.
Accordingly, there is a need in the art for a dual mode communication device and a method for operating such a device which solves these problems.